Diffusion Tensor Imaging in Alzheimer's disease

Attentional control and Information processing speed are central concepts in cognitive psychology and neuropsychology. Functional neuroimaging and neuropsychological assessment have depicted theoretical models considering attention as a complex and non-unitary process. One of its component processes, Attentional set-shifting ability, is commonly assessed using the Trail Making Test (TMT). Performance in the TMT decreases with increasing age in adults, Mild Cognitive Impairment (MCI) and Alzheimer’s Disease (AD). Besides, speed of information processing (SIP) seems to modulate attentional performance. While neural correlates of attentional control have been widely studied, there are few evidences about the neural substrates of SIP in these groups of patients. Different authors have suggested that it could be a property of cerebral white matter, thus, deterioration of the white matter tracts that connect brain regions related to set-shifting may underlie the age-related, MCI and AD decrease in performance. The aim of this study was to study the anatomical dissociation of attentional and speed mechanisms. Diffusion tensor imaging (DTI) provides a unique insight into the cellular integrity of the brain, offering an in vivo view into the microarchitecture of cerebral white matter. At the same time, the study of ageing, characterized by white matter decline, provides the opportunity to study the anatomical substrates speeded or slowed information processing. We hypothesized that FA values would be inversely correlated with time to completion on Parts A and B of the TMT, but not the derived scores B/A and B-A

Enfermedad cerebral, conectividad, plasticidad y terapia cognitiva. Una visión neurológica del trastorno mental

Resumen: Introducción: La relación entre mente y cerebro ha evolucionado desde el clásico dualismo hasta los conocimientos actuales que ponen de manifiesto que las funciones mentales son el resultado de la actividad cerebral. Este cambio de paradigma, junto con los recientes avances en diferentes técnicas de neuroimagen, ha dado lugar a una novedosa concepción del funcionamiento cerebral en términos de conectividad estructural y funcional. El objetivo del presente trabajo es describir la relación entre conectividad, lesión cerebral, plasticidad cerebral y recuperación funcional. Desarrollo: Si la función cerebral surge de la organización en red del cerebro como un todo, la disfunción cerebral se puede producir por una alteración en la conexión de estas redes. Así, a partir del modelo conectivista, los trastornos cognitivos y del comportamiento que aparecen tras una afección cerebral se describen como consecuencia de una alteración en la organización funcional de las redes cerebrales. Sin embargo, la pérdida de funciones puede ser recuperada gracias a la capacidad de los circuitos de ser dinámicos y versátiles. La plasticidad cerebral permite una reorganización funcional que llevará a una recuperación, espontánea o potenciada con terapia cognitiva, después de algún tipo de enfermedad cerebral. Conclusiones: El conocimiento de la conectividad y la plasticidad cerebrales proporciona una nueva perspectiva desde la que entender el funcionamiento cerebral en condiciones normales, los mecanismos del daño cerebral y los de la recuperación funcional, constituyendo las bases para el desarrollo de la terapia cognitiva. Abstract: Introduction: Our conception of the mind-brain relationship has evolved from the traditional idea of dualism to current evidence that mental functions result from brain activity. This paradigm shift, combined with recent advances in neuroimaging, has led to a novel definition of brain functioning in terms of structural and functional connectivity. The purpose of this literature review is to describe the relationship between connectivity, brain lesions, cerebral plasticity, and functional recovery. Development: Assuming that brain function results from the organisation of the entire brain in networks, brain dysfunction would be a consequence of altered brain network connectivity. According to this approach, cognitive and behavioural impairment following brain damage result from disrupted functional organisation of brain networks. However, the dynamic and versatile nature of these circuits makes recovering brain function possible. Cerebral plasticity allows for functional reorganisation leading to recovery, whether spontaneous or resulting from cognitive therapy, after brain disease. Conclusions: Current knowledge of brain connectivity and cerebral plasticity provides new insights into normal brain functioning, the mechanisms of brain damage, and functional recovery, which in turn serve as the foundations of cognitive therapy. Palabras clave: Plasticidad cerebral, Daño cerebral, Terapia cognitiva, Alteraciones del comportamiento, Trastornos mentales, Keywords: Brain plasticity, Brain damage, Cognitive therapy, Behaviour disorders, Mental disorder